Computer systems may run virtual machines with memory allocated by a hypervisor. With memory overcommit, virtual machines and their associated guest operating systems may “think” that they have access to more memory than is actually assigned by the hypervisor. For example, memory overcommit (or overcommitment) is a hypervisor feature that allows a virtual machine, in effect, to use more memory space than the physical host has available. To achieve memory overcommit, memory may be reallocated by adding and/or removing memory from other virtual machines as physical memory permits.